HIGH STRENGTH, HEAT RESISTANCE AND ABRASION RESISTANCE Cu-Mg-Sn ALLOY CONDUCTOR

Abstract: A Cu-Mg-Sn alloy conductor which exhibits high electric conductivity, high strength, heat resistance and abrasion resistance to be suitable to conductors for railway. The copper alloy of the invention consists of Mg of 0.1-0.5 wt.% and Sn of 0.1-0.6 wt.% in which sum of Mg and Sn must not exceed 0.7 wt.%.

Description: HIGH STRENGTH, HEAT RESISTANCE AND ABRASION RESISTANCE Cu-Mg-Sn ALLOY CONDUCTOR BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a Cu alloy material, and more particularly to a Cu-Mg-Sn alloy conductor which exhibits high electric conductivity, high strength, heat resistance and abrasion resistance to be suitable to conductors for special electric wires such as wires for an electric railway and an automobile, lead frames and the like. Description of the Prior Art A conventional conductor for an electric wire used in the field of electric railway must be basically satisfied in view of electric conductivity and abrasion resistance because manner for applying current to a railway car is fulfilled by contact of a trolley wire functioning as a lead-in wire and a pantagraph mounted on the railway car. During operation of the railway car, a friction between the trolley wire and the pantagraph is continuously generated. As the operation of the railway car is continued, the friction of the trolley wire is increased. Accordingly, abrasion resistive property of the wire material is a significant factor determining a service life of the trolley wire. In general, a hardened copper trolley wire produced by causing a pure copper to be subjected to cold working to have strength of about 35-44 kgf/mπr and abrasion resistance or a copper-silver trolley wire produced by adding a small amount of silver to a pure copper to improve its heat resistance has been broadly used. However, since the hardened copper or the copper-silver trolley wire requires frequent substitution works, there are problems in safety and management of the railway car system as a mass transportation. In recent, a copper-tin alloy or a copper-cadmium alloy and the like as an abrasion resistance trolley wire has been developed and used in place of the hardened trolley wire or the copper-silver trolley wire. Although the copper-cadmium alloy is favorable in that the alloy has a high electric conductivity above 80% IACS (International Annealed Copper Standard) and a tensile strength of 50kgf/mπr or more, its manufacturing cost is very high and it causes environmental pollution because the alloy must contain harmful heavy metal cadmium. Furthermore, although the copper-tin alloy which is a solid solution type of alloy containing tin of about 0.3- 0.7wt% to meet requirement of the wire for railway exhibits tensile strength of 40-45kgf/mπr and solid solution hardening effect, its electric conductivity is relatively low, that is, 60-70% IACS and the alloy is liable to be corroded under the saltish environment such as a seaside area, a snow melting agent distributed area and an industrial complex area. SUMMARY OF THE INVENTION The present invention has been made in view of the above- described problems occurring in the prior art and an object of the invention is to a Cu-Mg-Sn alloy conductor which exhibits high electric conductivity, high strength, heat resistance and abrasion resistance to be suitable to an electric conductor. In accordance with the present invention, the object mentioned above can be accomplished by providing a Cu-Mg-Sn alloy conductor consisting of 0.1wt% to 0.5wt% magnesium, 0.1wt% to 0.6wt% tin and the balance copper in which sum of the magnesium and tin does not exceed 0.7wt%. BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, features and advantages of the invention will become more apparent upon a reading of the following detailed specification and drawings, in which: Fig. 1 is a graph showing variance of tensile strength of the invention according to contents of Mg and Sn and work amount; and Fig. 2 is a graph showing variance of conductivity of the invention according to contents of Mg and Sn and work amount. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A copper alloy according to the present invention is a Cu-Mg-Sn ternary alloy which is produced by adding Mg and Sn of small amount to Cu. A Mg which is an alloying element of the Cu-Mg-Sn ternary alloy according to the invention is one of typical light metals (specific gravity 1.74). The Mg element is relatively inexpensive and nontoxic. Also, its small addition does not cause a conductivity of the resulting alloy to be degraded and causes a strength of the resulting alloy to be increased by cold working because the Mg element is excellent in work hardening effect. Furthermore, since the Mg element has high affinity for oxygen, sufficient deoxidation effect can be obtained without the deoxidation treatment by phosphor which is apt to cause degradation of the conductivity, and a corrosion resistance of the resulting alloy is improved by reducing remaining oxygen amount. On the other hand, the Mg element is not sufficiently mixed with copper during melting of the copper alloy because of high specific gravity difference between the copper and the magnesium. Also, since the Mg element causes the fluidity of the molten metal to be deteriorated severely, casting workability is decreased and it may cause the resulting alloy to be brittle because of its excessive deoxidation. For overcoming the above problems, the copper alloy of the invention is added with the Sn element. The Sn element has high affinity for copper and causes the Mg element to be alloyed easily. Also, the Sn element improves abrasion resistance of the resulting copper alloy and improves castability due to improvement of fluidity of molten metal. Furthermore, the Sn element compensates brittleness due to the Mg. A representative method for hardening metal by alloying treatment includes the solution hardening and precipitation hardening. The solid solution type of alloy largely varies in various physical properties according to increment of added elements. In particular, electrical property of the alloy is deteriorated. In general, the precipitation type of alloy is slightly deteriorated in electrical property and is improved in heat resistance. Hence, the precipitation type of alloy is mostly applied to in electric and electronic materials requiring high conductivity but the alloy is undesirable in view of economical point because the process for producing the alloy requires always the solution treatment and precipitation treatment and is also insufficient in mechanical strength. Accordingly, the present invention provides a solution hardening type of Cu-Mg-Sn ternary alloy which contains a small amount of Mg and Sn within a predetermined range by which the electrical property of the alloy is not deteriorated largely. Referring to Figs. 1 and 2, there are shown graphs showing variances of tensile strength and conductivity of the Cu-Mg-Sn ternary alloy of the invention according to content of Mg-Sn and deformation degree. As illustrated in the graphs, the copper alloy conductor, produced by the--£nvention exhibits a high conductivity of 60%-80%IACS (International Annealed Copper Standard) and a mechanical strength of 40kgf/mm - 80kgf/mm . In particular, the copper alloy of the invention is superior to a conventional alloy in abrasion resistance and heat resistance. Examples of the present invention will now be described in detail. Figs. 1 and 2 show variances of tensile strength and conductivity according to an amount of added alloying elements. As illustrated in the Figs. 1 and 2, when the Mg of o.5wt% or more is added, electrical conductivity of the resulting alloy is rapidly deteriorated. When the Sn of 0.6wt% or more is added, the tensile strength is not improved but only the conductivity is deteriorated. Also, when an amount of the added Mg or Sn is not more than 0.1wt%, the conductivity is favorable but remarkable improvement of mechanical property is not achieved. In view of the above fact, the copper alloy of the invention is designed to contain Mg of 0.1-0.5wt% and Sn of 0.1-0.6wt% in which sum of Mg and Sn must not exceeds 0.7wt%. In order to confirm various properties of the copper alloy of the invention, three ternary alloys having compositions of Cu-0.2wt%Mg-0.lwt%Sn, Cu-0.lwt%Mg-0.lwt%Sn and Cu-0.3wt%Mg-0.1wt%Sn were prepared and then made into trolley wires and catenary wires for railway. The trolley wires and the catenary wires of the invention were compared with trolley wires and catenary wires made of conventional copper alloys in various properties. Since the products to be compared in this examples are long electric wires, the copper alloys were cast into rods having a diameter of ø23mro by the horizontal continuous casting method. Alternatively, although the rods are made by another methods such as the semicontinuous casting method, the resulting rods have not differences of various properties. In alloying treatment of Sn and Mg, master alloy of 20wt%Mg-Cu was used as Mg element and pure Sn was used as Sn element. During melting of the metals, the molten metal was covered with sufficient amount of charcoal and maintained under inert atmosphere of nitrogen gas (N 2 ) so as to prevent the molten metal from being exposed to the air atmosphere. For deoxidation of the metal, a predetermined amount of Mg considering oxidation loss was charged and oxidized slag was removed. In the cast rods having a diameter of 023mm, the two rods having the compositions of Cu-0.2wt%Mg-0.lwt%Sn and Cu- 0.lwt%Mg-0.lwt%Sn were made into trolley wires of standard 110 sq. by wire drawing, and the two rods having the compositions of Cu-0.3wt%Mg-0.lwt%sn and Cu-0.2wt%Mg-0.lwt%Sn were directly made into wires of ø1.5mm by wire drawing without intermediate heat treatment. Table 1 shows comparison of trolley wires made of Cu- 0.2wt%Mg-0.1wt%Sn and Cu-0.lwt%Mg-0.lwt%Sn of the invention with trolley wires made of prior hard copper and Cu-Sn alloy in tensile strength, conductivity, abrasion resistance and heat resistance. In the comparison test, the abrasion test was carried out in such a manner that a cylindrical specimen having diameter 8mm and length 12mm and prepared from the above trolley wire is brought into contact at its longitudinal surface with a high speed steel disk having a diameter of 100mm, the high speed steel is rotated ten thousand times at 600RPM and a weight loss of the specimen is measured. At this time, aqueous cutting oil is used as lubricant. The heat resistance test was carried out in such a manner that a specimen is maintained in a furnace of 300 * C under argon gas atmosphere for 2 hours, cooled by water and measured in tensile strength, and a value of the tensile strength after the heat treatment divided by a tensile strength prior to the heat treatment is represented by the percentage. Table 2 shows comparison of catenary wires made of Cu- 0.3wt%Mg-0.1wt%Sn and Cu-0.2wt%Mg-0. lwt%Sn of the invention with catenary wires made of prior Cu-Cd alloy and Cu-Sn alloy in tensile strength, conductivity and heat resistance. In this comparison test, the heat resistance test was carried out in a manner similar to that of the test carried in Table 1 except that the maintaining temperature and time are different from those in Table 1. Table 1 Comparison of Properties of Trolley Wires for Railway Tensile Conductivi y Abrasion Heat Strength Resistance Resistance (kgf/mm 2 ) (XIACS) (abrasion (300'C X 2hr) loss mg) Hard Copper wire 36-38 97T 8.9 62% Cu-0.3%Sn wire 38-43 75-76 7.3 90% Cu-0.2XMg-0.1%Sn wire 43-47 73-75 5.4 92% Cu-0.1XMg-0.1XSn wire 38-43 78-80 7.4 94% Table 2 Comparison of Properties of Catenary Wires for Railway Tensile Conductivity Heat Strength Resistance (kgf/mm 2 ) (%IACS) (400 * C X 30min) Cu-0.8XCd wire 62 801 66% Cu-0.8%Cd-0.3%Sn wire 65-70 62! 72% Cu-0.3%Sn wire 58-62 731 72% Cu-0.3%Mg-0.1%Sn wire 68-72 651 71% Cu-0.2XMg-0.1XSn wire 63-64 721 73% As apparent from Tables 1 and 2, the copper alloy of the invention is superior to a conventional copper alloy in various properties. In particular, it will be appreciated that various properties of the copper alloy of the invention are almost equal to or superior to those of a Cu-Cd alloy in which the Cd is a representative heavy metal and causes an environmental pollution and an uneconomical factor from its manufacturing process. On the other hand, since Cu-Zr alloy, Cu-Cr-Zr alloy and the like which are broadly used for a lead frame, a special wire conductor, an electrode and the like are hardened by the precipitation hardening, its manufacturing process requires solution treatment and precipitation treatment, thereby causing an uneconomical factor. Accordingly, it will be appreciated that the copper alloy according to the invention can be substituted for a prior copper alloy containing Cd and exhibits various properties superior to a prior heat treatment type of copper alloy and economical advantages, so that the copper alloy of the invention is sufficiently competitive. While the subject invention has been described with respect to a particularly preferred embodiment, it will be apparent to those skilled in the art that certain modification may be made which are intended to be within the scope of the appended calms.

Claims: WHAT IS CLAIMED IS: 1. A Cu-Mg-Sn alloy conductor consisting of 0.1wt% to 0.5wt% magnesium, 0.1wt% to 0.6wt% tin and the balance copper. 2. A cu-Mg-Sn alloy conductor according to Claim 1, wherein sum of the magnesium and tin does not exceed 0.7wt%. 3. A cu-Mg-Sn alloy conductor according to Claim 1 or 2, wherein the alloy conductor is produced by a horizontal continuous casting method. 4. A cu-Mg-Sn alloy conductor according to Claim 1 or 2, wherein the alloy conductor is produced by being subjected to a hot working and a cold working by a semicontinuous casting method. AMENDED CLAIMS [received by the International Bureau on 7 June 1995 (07.06.95); original claim 4 amended; remaining claims unchanged (1 page)] 1. A Cu-Mg-Sn alloy conductor consisting of 0.1vtt to 0.5vtt magnesium, O.lvtt to O.δvtt tin and the balance copper. 2. A Cu-Mg-Sn alloy conductor according to Claim 1, vherein sum of the magnesium and tin does not exceed 0.7vtt. 3. A Cu-Mg-Sn alloy conductor according to Claim 1 or 2 , vherein the alloy conductor is produced by a horizontal continuous casting method. 4. A Cu-Mg-Sn alloy conductor according to Claim 1 or 2, vherein the alloy conductor is produced by being subjected to a semicontinuous casting method folloved by a hot vorking and a cold vorking.

Inventors: HAN KWANG HYOUN, JOO EUN SUK, KIM DONG KEE, KIM SANG KYOUM, PARK JONG CHUN, YOON YOUNG JIN, HAN, KWANG, HYOUN, JOO, EUN, SUK, KIM, DONG, KEE, KIM, SANG, KYOUM, PARK, JONG, CHUN, YOON, YOUNG, JIN
Applicants: GOLD STAR CABLE CO LTD, HAN KWANG HYOUN, JOO EUN SUK, KIM DONG KEE, KIM SANG KYOUM, PARK JONG CHUN, TAIHAN ELECTRIC WIRD, YOON YOUNG JIN, GOLDSTAR CABLE CO., LTD., HAN, KWANG, HYOUN, JOO, EUN, SUK, KIM, DONG, KEE, KIM, SANG, KYOUM, PARK, JONG, CHUN, TAIHAN ELECTRIC WIRE CO., LTD., YOON, YOUNG, JIN
Application year: 1994
Main classification: H01B1
IPC codes: C22C9, H01B1